diff --git a/proc.c b/proc.c
index 0f7f159..a016cd4 100644
--- a/proc.c
+++ b/proc.c
@@ -126,6 +126,7 @@ copyproc(struct proc *p)
       kfree(np->kstack, KSTACKSIZE);
       np->kstack = 0;
       np->state = UNUSED;
+      np->parent = 0;
       return 0;
     }
     memmove(np->mem, p->mem, np->sz);